JP2023089105A - Methods for synthesizing and using ald precursors of molybdenum or tungsten containing thin films - Google Patents

Abstract

To provide precursors and methods for forming thin films comprising molybdenum or tungsten by atomic layer deposition.SOLUTION: Processes for forming Mo and W containing thin films, such as MoS2, WS2, MoSe2, and WSe2 thin films are provided. Methods are also provided for synthesizing Mo or Wβ-diketonate precursors. Additionally, methods are provided for forming 2D materials containing Mo or W.SELECTED DRAWING: Figure 1

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is filed June 17, 2015 and U.S. Provisional Patent Application No. 62/167,220, filed May 27, 2015, under 35 U.S.C. No. 62/167,220, the entire contents of which are hereby incorporated by reference.

Parties to a Joint Research Agreement The invention claimed in this application is made by or for and/or to a joint research agreement between the University of Helsinki and ASM Microchemistry Oy. made in relation to This Agreement was in force on and before the date the claimed invention was made, and the claimed invention was made as a result of activities undertaken within the scope of this Agreement.

The present application relates generally to precursors and methods for forming thin films comprising molybdenum or tungsten by atomic layer deposition. Such films may find use, for example, as two-dimensional (2D) materials in electronic devices.

Related Art Conventional processes for atomic layer deposition (ALD) of all kinds of thin films containing molybdenum use a select few known molybdenum precursors such as MoCl ₅ , Mo(CO) ₆ as well as Mo(N ^t Bu) ₂ It has been limited to alkylamine precursors such as (NMe ₂ ) ₂ and Mo(N ^t Bu) ₂ (NEt ₂ ) ₂ . Recently reported precursor combinations for the deposition of _MoS2 thin films include Mo(CO) ₆ and _H2S , Mo(CO) ₆ and MeSSMe, and _MoCl5 and _H2S . However, these conventional molybdenum precursors can prove difficult to handle. For example, Mo(CO) ₆ is a highly toxic substance with a narrow deposition temperature range that would be too low to deposit molybdenum-containing crystalline thin films. MoCl ₅ , on the other hand, appears to require additional residence time to successfully deposit MoS ₂ films.

Some Mo alkylamine precursors can contain Mo with an oxidation state of +VI, which can cause problems during the deposition of all kinds of molybdenum-containing thin films. Mo alkylamine precursors with an oxidation state of +IV, where Mo is more preferred, are generally unstable and difficult to use. In addition, Moalkylamine precursors are relatively temperature sensitive and decompose at low temperatures. This can lead to decomposition of the Moalkylamine precursors, as relatively high temperatures are usually required to promote crystalline film growth. This decomposition can produce impurities such as carbon that can retard or even prevent the crystallization of all types of molybdenum-containing thin films.

Molybdenum(III) β-diketonates have been utilized to deposit Mo-containing thin films using chemical vapor deposition (CVD) processes, but have not been extensively investigated for use in ALD type processes. A previously disclosed process for the synthesis of molybdenum (III) β-diketonates uses Mo(CO) ₆ , K ₃ MoCl ₆ and (NH ₄ ) ₂ [MoCl ₅ (H ₂ O)]. Each of these compounds has significant drawbacks and can prove difficult to handle. For example, as mentioned above, Mo(CO) ₆ is highly toxic and highly volatile, adding to the difficulty of the procedures used. Laboratory synthesis _{of K3MoCl6} is difficult and requires electrochemical or high temperature processes.

Transition metal dichalcogenide materials, especially 2D transition metal dichalcogenide materials such as Mo and W dichalcogenides, have desirable electrical properties for a variety of applications. Moreover, unlike graphene, another two-dimensional material, some two-dimensional transition metal dichalcogenides have direct bandgaps and are semiconducting. Therefore, two-dimensional transition metal dichalcogenides such as Mo and W dichalcogenides are being investigated for application to miniaturization of devices.

In some aspects, processes are provided for forming Mo or W containing thin films. In some embodiments, a Mo or W containing thin film is formed on a substrate within a reaction chamber in a process comprising at least one cycle. The cycle comprises contacting the substrate with a vapor phase Mo or W precursor such that at most a first Mo or W precursor monolayer is formed on the substrate surface; removing the W precursor and reaction by-products, if any; contacting the substrate with a vapor phase chalcogen precursor; excess chalcogen precursor and reaction by-products, if any; , removing it, and optionally repeating the contacting and removing steps until a desired thickness of Mo- or W-containing thin film is formed. In some embodiments, Mo or W in the Mo or W precursor has an oxidation state below +IV but not 0. In some embodiments, chalcogen precursors react with Mo or W precursors on the substrate surface.

In some embodiments, the process is an atomic layer deposition (ALD) process. In some embodiments, the process includes two or more consecutive cycles. In some embodiments, the Mo or W containing thin film is a Mo or W sulfide, selenide, or telluride thin film. In some embodiments, the oxidation state of Mo or W in the Mo or W precursor is +III. In some embodiments, the chalcogen precursor comprises _H2S , _H2Se , _H2Te , ( _CH3 ) _2S , ( _CH3 ) _2Se , or ( _CH3 ) _2TSe .

In some aspects, atomic layer deposition (ALD) processes for forming Mo or W sulfide, selenide, or telluride thin films are provided. According to some embodiments, a Mo or W sulfide, selenide or telluride thin film is formed on a substrate in a reaction chamber with an ALD process comprising at least one cycle. The cycle comprises contacting the substrate with a vapor phase Mo or W precursor such that at most a first Mo or W precursor monolayer is formed on the substrate surface; removing the W precursor and reaction by-products, if any; contacting the substrate with a vapor phase chalcogen precursor; excess chalcogen precursor and reaction by-products, if any; , removing it, and repeating the contacting and removing steps until a desired thickness of Mo- or W-containing thin film is formed. In some embodiments, the Mo or W precursor may contain at least one bidentate ligand. In some embodiments, chalcogen precursors react with Mo or W precursors on the substrate surface.

In some embodiments, the bidentate ligand is attached to the Mo or W atom through an O, S, or N atom. In some embodiments, the bidentate ligand is attached to the Mo or W atom through two O atoms. In some embodiments, the bidentate ligand is attached to the Mo or W atom through an O and N atom. In some embodiments, the bidentate ligand is attached to the Mo or W atom through two N atoms. In some embodiments, the bidentate ligand is a β-diketonato ligand. In some embodiments, the β-diketonato ligand is an acetylacetonato (acac) ligand. In some embodiments, the β-diketonato ligand is a 2,2,6,6-tetramethyl-3,5-heptanedionato (thd) ligand. In some embodiments, the Mo or W precursor comprises at least two bidentate ligands. In some embodiments, the Mo or W precursor contains three bidentate ligands.

In some aspects, atomic layer deposition (ALD) processes for forming Mo or W sulfide, selenide, or telluride 2D materials are provided. According to some embodiments, a Mo or W sulfide, selenide, or telluride 2D material is formed on a substrate in a reaction chamber with an ALD process that includes at least one cycle. The cycle comprises contacting the substrate with a vapor phase Mo or W precursor such that at most a first Mo or W precursor monolayer is formed on the substrate surface; removing W precursors and reaction by-products, if any; contacting the substrate with gas phase sulfur, selenium or tellurium precursors; removing excess sulfur, tellurium or selenium precursors and reaction; and removing by-products, if any. In some embodiments, the Mo or W precursor is a Mo or W β-diketonate precursor. In some embodiments, sulfur, selenium or tellurium precursors react with Mo or W precursors on the substrate surface.

In some aspects, processes are provided for forming Mo or W sulfide, selenide, or telluride 2D materials. According to some embodiments, a Mo or W sulfide, selenide, or telluride 2D material is formed on a substrate within a reaction chamber in a cyclic process comprising at least one cycle. The cycle is such that up to a monolayer of Mo or W containing material, preferably no more than about 50% of the monolayer, preferably no more than about 25% of the monolayer, more preferably less than about 10% of the monolayer, is on the substrate surface. and exposing the substrate to a purge gas, and/or if there is excess Mo or W precursor and reaction by-products, such that the substrate is formed in contacting the substrate with vapor phase sulfur, selenium or tellurium precursors; exposing the substrate to a purge gas; and/or removing excess sulfur, tellurium or selenium precursors and and removing reaction by-products, if any. In some embodiments, the Mo or W precursor is a Mo or W β-diketonate precursor. In some embodiments, sulfur, selenium or tellurium precursors react with Mo or W containing materials deposited on the substrate surface.

In some embodiments, the Mo or W containing thin film is a Mo or W sulfide, selenide, or telluride thin film. In some embodiments, the oxidation state of Mo or W atoms, including Mo or W precursors, is +III. In some embodiments, the chalcogen precursor comprises _H2S , _H2Se , _H2Te , ( _CH3 ) _2S , ( _CH3 ) _2Se , or ( _CH3 ) _2Te . In some embodiments, the Mo or W precursor is Mo(thd) ₃ and the chalcogen precursor is _H2S . In some embodiments, the Mo or W precursor is W(thd) ₃ and the chalcogen precursor is _H2S . In some embodiments, the 2D material comprises _MoS2 .

In some aspects, methods of making Mo or W β-diketonate precursors are provided. According to some embodiments, the Mo or W β-diketonate precursor has the formula MX ₃ (R)n ₃ , where n is a number from 0 to 4, M is Mo or W, X is a halide and R is a solvent; reacting an alkali metal compound with a β-diketonate compound to form a first product; and adding the first product to the first reactant. In some embodiments, Mo or W β-diketonate precursors are formed having the formula ML ₃ , where M is Mo or W and L is a β-diketonato ligand.

In some embodiments, providing a first reactant comprises reducing a Mo or W halide with a reducing agent to form a first intermediate product, followed by a solvent It can further include forming a second intermediate product by adding to the product, thereby forming the first reactant. In some embodiments, the Mo or W halide is MoCl ₅ , the β-diketone compound is Hthd, and the Mo or W β-diketonate precursor formed is Mo(thd) ₃ .

In some aspects, methods of forming Mo or W β-diketonate compounds are provided. According to some embodiments, the Mo or W β-diketonate compound has the formula MX ₃ (R)n ₃ , where n is a number from 0 to 4, M is Mo or W, X is a halide and R is a solvent), reacting an alkali metal compound with a β-diketonato compound to form a first product, followed by and reacting the first product with the first reactant. In some embodiments, a Mo or W β-diketonate compound having the formula ML ₃ , where M is Mo or W with an oxidation state of +III and L is a β-diketonato ligand It is formed. In some embodiments, Mo or W in the Mo or W β-diketonate compound has a +III oxidation state.

In some aspects, processes are provided for forming Mo- or W-containing materials. According to some embodiments, a Mo- or W-containing material is formed on a substrate in a reaction chamber in a process that includes at least one deposition cycle, which cycle converts the substrate to vapor phase Mo or W. Alternately and sequentially contacting the precursor and the second vapor phase chalcogen precursor. In some embodiments, Mo or W in the Mo or W precursor has an oxidation state below +IV but not 0.

In some embodiments, deposition is repeated two or more times. In some embodiments, after contacting the substrate with the gas phase Mo or W precursor and before contacting the substrate with the gas phase chalcogen precursor, excess Mo or W precursor and reaction by-products are removed. If there is, remove it. In some embodiments, excess chalcogen precursor and reaction by-products, if any, are removed after contacting the substrate with the vapor phase chalcogen precursor and before initiating another deposition cycle. to remove In some embodiments, the substrate is contacted with a purge gas after contacting the substrate with the Mo or W gas phase precursor and before contacting the substrate with the gas phase chalcogen precursor. In some embodiments, the substrate is contacted with a purge gas after contacting the substrate with the chalcogen gas phase precursor and before initiating another deposition cycle. In some embodiments the Mo or W containing material comprises the Mo or W element. In some embodiments, the Mo or W containing material comprises a Mo or W oxide material. In some embodiments, the Mo or W containing material comprises a Mo or W nitride material. In some embodiments, the Mo or W containing material comprises a Mo or W silicide material.

The invention will be better understood from the detailed description and from the accompanying drawings, which are intended to illustrate the invention and are not intended to limit the invention.

1 is a process flow diagram generally illustrating a method of depositing Mo or W containing thin films; FIG. 1 is a process flow diagram generally illustrating a method of synthesizing metal β-diketonate precursors. FIG. 2 is a mass spectrum of a sample of Mo(thd) ₃ synthesized according to the procedures described herein. Figure 3 illustrates the molecular structure of Mo(thd) ₃ determined by single crystal X-ray diffraction. Figure 3 illustrates thermogravimetric curves for Mo(acac) ₃ , Mo(hfac) ₃ , and Mo(thd) ₃ . ₂ is a Field Emission Scanning Electron Microscope (FESEM) image of MoS2 thin films. Fig _{. 2} is a graph of growth rate per cycle of MoS2 thin films versus pulse length of Mo(thd) ₃ and _H2S precursors; 4 is a graph of film thickness versus number of deposition cycles; A series of field emission scanning electron microscope (FESEM) images of _MoS2 thin films deposited at 500° C. using various Mo(thd) ₃ precursor pulse lengths. 4 is a series of Field Emission Scanning Electron Microscope (FESEM) images of _MoS2 thin films deposited at 500° C. using various _H2S precursor pulse lengths. Figure ₂ is a series of Field Emission Scanning Electron Microscope (FESEM) images of MoS2 thin films deposited at 500°C with 10-50 deposition cycles. 2 is a series of Field Emission Scanning Electron Microscope (FESEM) images of MoS ₂ thin films deposited at 500° C. with 100-2000 deposition cycles. 4 is a graph of the composition of _MoS2 thin films deposited with varying Mo(thd) ₃ precursor pulse lengths measured by energy dispersive X-ray (EDX) analysis. Figure ₂ is a graph of the composition of MoS2 thin films deposited with varying _H2S precursor pulse lengths measured by energy dispersive X-ray (EDX) analysis; MoS ₂ film thickness versus number of deposition cycles, and elemental fractions of Mo and S versus number of deposition cycles are illustrated. Figure 2 shows grazing incidence X-ray diffraction (GIXRD) patterns of _MoS2 thin films deposited with various chalcogen and Mo precursor pulse lengths. Raman spectra of _MoS2 thin films. Figure 4 illustrates Raman spectra of _MoS2 thin films deposited with various chalcogen and Mo precursor pulse lengths. Figure 3 illustrates the elemental composition of two _MoS2 thin films analyzed by X-ray photoelectron spectroscopy (XPS). Figure 3 illustrates the surface roughness of MoS2 thin films analyzed using atomic force microscopy (AFM). Figure 3 illustrates the growth rate of MoS ₂ thin films and the elemental ratio of Mo and S versus deposition temperature. A series of Field Emission Scanning Electron Microscope (FESEM) images of _MoS2 thin films deposited between 350°C and 500°C. Fig _{. 2} is an aberration-corrected scanning tunneling electron microscope (AC-STEM) image of a MoS2 thin film deposited on a silicon substrate containing native oxide.

As described below, Mo and W containing thin films can be deposited on substrates by atomic layer deposition (ALD) type processes. In some embodiments, Mo or W chalcogenide thin films, particularly Mo or W sulfide or selenide thin films, can be deposited on a substrate by an ALD type process. ALD-type processes are based on controlled surface reactions of precursor chemicals. Gas phase reactions are avoided by alternately and continuously contacting the substrate with the precursor. Vapor phase reactants are separated from each other on the substrate surface, for example, by removing excess reactants and/or reactant by-products from the reaction chamber between reactant pulses.

Suitable substrate materials may include insulating materials, dielectric materials, crystalline materials, epitaxial, heteroepitaxial, or monocrystalline materials such as oxides. For example, the substrate may comprise Al ₂ O ₃ , sapphire, silicon oxide, or insulating nitrides such as AlN. Additionally, the substrate material and/or substrate surface can be selected by one skilled in the art to enhance, increase, or maximize two-dimensional crystal growth thereon. In some embodiments, the substrate surface on which the Mo and W containing thin film or material is deposited is free of semiconductor materials such as Si, Ge, III-V compounds such as GaAs and InGaAs, and II-VI compounds. . In some embodiments, the substrate surface on which the Mo and W containing thin film or material is deposited may also include materials other than insulating materials. In some embodiments, after deposition of the Mo or W containing thin film, the Mo and W containing thin film is removed from at least a portion of the substrate comprising materials other than the insulating material. In some embodiments, the substrate surface on which the Mo and W containing film or material, preferably the Mo or W chalcogenide film or material is deposited, comprises sulfur, a chalcogen such as selenium or tellurium, most preferably sulfur. . In some embodiments, the substrate surface on which the Mo and W containing thin film or material is deposited comprises surface groups comprising chalcogen, preferably surface groups with chalcogen-hydrogen bonds such as --SH groups.

Briefly, the substrate is heated to a suitable deposition temperature, typically under reduced pressure. The deposition temperature is generally maintained below the thermal decomposition temperature of the reactants, but at a level high enough to avoid condensation of the reactants and to provide the activation energy for the desired surface reactions. be done. Of course, the appropriate temperature window for any given ALD reaction depends on the surface termination and reactant species involved. Here, the temperature will vary depending on the type of film being deposited and the particular precursor, but is preferably no greater than about 650°C, more preferably less than about 500°C. The temperature window is preferably from about 250°C to about 600°C, more preferably from about 350°C to about 550°C, most preferably from about 375°C to about 500°C. Optionally, the reaction temperature is above about 250°C, preferably above about 350°C, and most preferably above about 375°C.

In some embodiments, the deposition temperature may exceed the decomposition temperature of the reactants, but still provide reasonably surface-controlled growth of the film and less than or equal to about one monolayer of material per deposition cycle. May be low enough to maintain growth rate. In some embodiments, the deposition cycle growth rate is no greater than about 50%, preferably less than about 25%, more preferably less than about 10% of about one monolayer of material deposited per cycle. can be done.

In some embodiments, the deposition process may not be a pure ALD process. In some embodiments, the chalcogen precursor may flow continuously or substantially continuously through the reaction space during the deposition process. For example, the flow rate of the chalcogen precursor through the reaction space can be reduced while the substrate is in contact with the metal precursor. In some embodiments in which the chalcogen precursor can flow continuously, the growth rate of the film per pulse of the metal precursor is about 1 monolayer or less of the deposited material. In some embodiments in which the chalcogen precursor flows continuously, the growth rate per pulse of the metal precursor is about 50% or less, preferably less than about 25%, more preferably about less than 10%.

In some embodiments, the growth rate of Mo and W containing thin films is less than about 2 Å/cycle, less than about 1.5 Å/cycle, less than about 1 Å/cycle, or even less than about 0.5 Å/cycle. In some embodiments, the growth rate of Mo and W containing dichalcogenide thin films can be from about 0.025 Å/cycle to about 0.5 Å/cycle. In other embodiments, the growth rate of Mo and W containing dichalcogenide thin films, such as _MoS2 thin films, is between about 0.05 Å/cycle and about 0.3 Å/cycle.

In some embodiments, the substrate surface can be subjected to a pretreatment process. In some embodiments, the pretreatment process includes exposing the substrate to a pretreatment reactant, either in situ or ex situ, prior to depositing the Mo or W containing thin film. In some embodiments, the pretreatment process includes exposing the substrate surface to at least one of the following pretreatment reactants ( _NH4 ) _2S , _H2S , HCl, HBr, _Cl2 , and HF. can include In some embodiments, the pretreatment process can include exposing the substrate surface to plasma, atoms, or radicals. In some embodiments, the pretreatment process exposes the substrate surface to a chalcogen-containing plasma, atoms, or radicals, such as sulfur, selenium, or tellurium, preferably sulfur-containing plasma, atoms, or radicals. can include exposing. In some embodiments, the plasma, atoms, or radicals may contain tellurium. In some embodiments, the plasma, atoms or radicals may contain selenium. In some embodiments, the pretreatment process can include exposing the substrate surface to a chalcogen-containing plasma, atoms, or radicals present in subsequent deposition processes. In some embodiments, the pretreatment process includes exposing the substrate surface to plasma, atoms, or radicals formed from chalcogen compounds that include chalcogen-hydrogen bonds, such as plasma, atoms, or radicals formed from H ₂ S. and the like. In some embodiments, the pretreatment process can include exposing the substrate surface to at least one pretreatment reactant for about 1 second to about 600 seconds, preferably about 1 second to about 60 seconds. The pretreatment process may utilize pretreatment reactants in vapor form and/or liquid form. In some embodiments, pretreatment processes may occur at the same temperature and/or pressure as subsequent deposition processes. In some embodiments, the pretreatment process can be similar to the subsequent deposition process, except that the pretreatment process requires longer pulse or exposure times than used in the subsequent deposition process. In some embodiments, a pretreatment process can include exposing the substrate surface to a pretreatment reactant to form a desired surface termination, such as a --SH surface termination. In some embodiments, forming a desired surface termination, such as a --SH surface termination, can facilitate two-dimensional growth of Mo or W containing thin films or materials. In some embodiments, the pretreatment process forms the substrate from a plasma, atoms, or radicals free of S, Se, and Te, such as a plasma, atoms, or radicals containing hydrogen, such as _H2. Plasma. In some embodiments, the pretreatment process can include exposing the substrate to oxygen plasma, oxygen atoms, or oxygen radicals. In some embodiments, a pretreatment process can include exposing a substrate, such as a substrate comprising AlN, to nitrogen plasma, nitrogen atoms, or nitrogen radicals. In some embodiments, a pretreatment process can be used to clean the substrate surface prior to deposition of Mo or W containing films or materials.

The substrate surface is contacted with the gas phase first reactant. In some embodiments, a pulse of gas phase first reactant is supplied to a reaction space containing a substrate. In some embodiments, the substrate is transferred to a reaction space containing a gas phase first reactant. Preferably, the conditions are selected such that no more than about one monolayer of the first reactant is adsorbed onto the substrate surface in a self-limiting manner. Appropriate contact times can be readily determined by those skilled in the art based on the particular circumstances. Any excess first reactant and reaction by-products are removed from the substrate surface by purging with an inert gas or by removing the substrate from the presence of the first reactant .

Purging is performed by evacuating the chamber using a vacuum pump and/or replacing the gas in the reactor with an inert gas such as argon or nitrogen to remove the gas phase precursor material and/or the gas phase secondary material. It is meant to remove the product from the substrate surface. A typical purge time is about 0.05-20 seconds, more preferably about 0.2-10 seconds, more preferably about 0.5-5 seconds. However, if very high aspect ratio structures or other structures with complex surface morphology are required, or if a high degree of conformal step coverage is required, or a different reactor type such as a batch reactor is used. Other purge times may be utilized as desired.

The substrate surface is contacted with a second gaseous reactant in the vapor phase. In some embodiments, a pulse of the second gaseous reactant is supplied to the reaction space containing the substrate. A gas phase second gas reactant may be fed into the reaction chamber in a substantially continuous flow from the inlet to the outlet of the reaction chamber. In some embodiments, the exit flow from the reaction chamber, eg, the pump line, is not closed. In some embodiments, outlet flow from the reaction chamber, such as flow from the reaction chamber to the pump line and also flow through the pump line prior to the pump, is not substantially closed, but can be restricted. In some embodiments, the substrate is transferred to a reaction space containing a gas phase second reactant. Any excess second reactants and gaseous by-products of the surface reaction are removed from the substrate surface. In some embodiments, there is no residence time for reactants. In some embodiments, the vapor phase reactant is not static within the reaction space and the vapor phase reactant is in contact with the substrate. Vapor phase reactants are static if the reactants are not flowing against the substrate or if the reactants are flowing from one inlet into a reaction space with no open outlets. be able to.

The contacting and removing steps are repeated until a thin film of the desired thickness is selectively formed on the substrate with each cycle depositing about a monolayer or less. The steps of contacting and removing the first gas phase Mo or W precursor can be referred to as the first precursor phase, the Mo or W precursor phase, or the Mo or W phase. The steps of contacting and removing the second gas phase precursor can be referred to as the second precursor phase, the chalcogen precursor phase, or the chalcogen phase. Collectively, these two phases can constitute a deposition cycle. Additional phases, including alternating and sequential contacting of the substrate surface with other reactants, can be added to form more complex materials, such as ternary materials.

As mentioned above, each step of each cycle is preferably self-regulating. Excess reactant precursors are supplied at each stage to saturate the structural surfaces undergoing reaction. Surface saturation ensures reactant occupancy of all available reactive sites (e.g., subject to physical size or "steric hindrance" limitations), thus ensuring excellent step coverage and uniformity. to Typically, less than one monolayer of material is deposited in each cycle, but in some embodiments more than one monolayer is deposited during one cycle.

Removal of excess reactants may include evacuating a portion of the contents of the reaction space and/or purging the reaction space with helium, nitrogen, or other inert gas. In some embodiments, purging can include stopping the flow of reactive gas while the inert carrier gas continues to flow into the reaction space.

Precursors used in ALD-type processes can be solid, liquid or gaseous materials under standard conditions (room temperature and atmospheric pressure), provided that the precursors are in the gas phase prior to contact with the substrate surface. may Contacting the substrate surface with the vaporized precursor means that the precursor vapor contacts the substrate surface for a predetermined period of time. Typically, the contact time is about 0.05-20 seconds, more preferably about 0.2-10 seconds, still more preferably about 0.5-5 seconds. In some embodiments, the gas phase second gas contact time is preferably of the same order of magnitude as the gas phase first gas reactant contact time. In some embodiments, the vapor phase second gas contact time is preferably about 100 times or less greater than the vapor phase first gas reactant contact time.

However, depending on the type of substrate and its surface area, the contact time may be even longer than 20 seconds. Contact times may be on the order of minutes in some cases. One skilled in the art can determine the optimum contact time based on the particular circumstances. In some embodiments, the chalcogen precursor contact time is less than about 60 seconds, preferably less than about 30 seconds, more preferably less than about 10 seconds, and most preferably less than about 5 seconds.

A person skilled in the art can also determine the mass flow rate of the precursor. In some embodiments, the Mo or W precursor flow rate is preferably about 1-1000 seem, more preferably about 100-500 seem.

The pressure within the reaction chamber is typically from about 0.01 to about 50 mbar, more preferably from about 0.1 to about 10 mbar. Given the particular circumstances, the pressure may be higher or lower than this range, as can be determined by one of ordinary skill in the art.

Prior to initiating film deposition, the substrate is typically heated to a suitable growth temperature. The growth temperature varies depending on the type of thin film to be formed, the physical properties of the precursor, and the like. The growth temperature is preferably about 650° C. or less, more preferably about 500° C. or less. The growth temperature window is preferably from about 250°C to about 600°C, more preferably from about 350°C to about 550°C, and most preferably from about 375°C to about 500°C. In some cases, the growth temperature is greater than about 250°C, preferably greater than about 350°C, and most preferably greater than about 375°C. The growth temperature can be below the crystallization temperature of the deposition material, such that an amorphous thin film is formed, or it can be above the crystallization temperature, such that a crystalline thin film is formed. Preferred deposition temperatures are those of the substrate including, but not limited to, reactant precursors, pressure, flow rate, reactor geometry, crystallization temperature of the deposited thin film, and properties of the material being deposited. It can vary depending on many factors such as composition. A person skilled in the art can select a particular growth temperature. The thermal budget, ie the reaction temperature and optionally the annealing temperature at any point during deposition and further processing after deposition of the films of the present invention, is preferably less than about 800° C., more preferably about 650° C. C., most preferably less than about 600.degree. C., and sometimes less than about 500.degree.

In some embodiments, the deposited Mo- or W-containing thin film can undergo any post-deposition treatment process. In some embodiments, for example, a post-deposition treatment process can include an annealing process, such as a forming gas annealing process. In some embodiments, the post-deposition treatment process can include exposing the Mo or W containing thin film or material surface to plasma. In some other embodiments, the post deposition treatment process does not include exposing the Mo or W containing thin film or material surface to plasma.

In some embodiments, the post-deposition treatment process includes exposing the deposited Mo- or W-containing thin film or material to a post-deposition treatment reactant, either in situ or ex-situ. obtain. In some embodiments, the post deposition treatment process includes exposing the Mo or W containing thin film or material surface to at least one of the following post deposition treatment reactants: ( _NH4 ) _2S or _H2S . can include In some embodiments, the post-deposition treatment process can include exposing the Mo or W containing film or material to a chalcogen containing plasma, such as a sulfur containing plasma. In some embodiments, the post-deposition treatment process includes exposing the Mo- or W-containing thin film or material to a plasma formed from a chalcogen compound containing chalcogen-hydrogen bonds, such as a plasma formed from H ₂ S. can include In some embodiments, the post-deposition treatment process can include exposing the Mo or W containing film or material to a chalcogen containing plasma, such as a sulfur containing plasma. In some embodiments, the post deposition treatment process includes exposing the Mo or W containing film or material to at least one post deposition treatment reactant for about 1 second to about 600 seconds, preferably about 1 second to about 60 seconds. can include exposing. Post deposition treatment processes may utilize post deposition treatment reactants in vapor form and/or liquid form. In some embodiments, post-deposition treatment processes may occur at approximately the same temperature and/or pressure as subsequent deposition processes. In some embodiments, the post-deposition treatment process can be similar to the previous deposition process, except that it requires longer pulse or exposure times than used in the previous deposition process. In some embodiments, the post-deposition treatment process includes exposing the Mo- or W-containing thin film or material to a hydrogen-containing plasma, such as a plasma formed from atoms or radicals, such as _H2 .

Examples of suitable reactors that can be used include commercially available ALD equipment such as ASM America, Inc., Phoenix, Ariz. , ASM Japan KK, Tokyo, Japan, and Almere ASM Europe B.V. V. and F-120® reactors, Eagle® XP8, Pulsar® reactors, and Advance® 400 Series reactors commercially available from Epson. In addition to these ALD reactors, many other types of reactors capable of ALD growth of thin films can be used, including CVD reactors with appropriate equipment and means for pulsing the precursors. can. In some embodiments, a flow ALD reactor is used. Preferably, the reactants are kept separate until they reach the reaction chamber so that shared lines for precursors are minimized. However, prior reactions such as those described in U.S. patent application Ser. Other configurations, such as the use of chambers, are also possible, the disclosures of which are incorporated herein by reference.

In some embodiments, a suitable reactor may be a batch reactor and may contain more than about 25 substrates, more than about 50 substrates, or more than about 100 substrates. In some embodiments, a suitable reactor may be a mini-batch reactor, containing from about 2 to about 20 substrates, from about 3 to about 15 substrates, or from about 4 to about 10 substrates. obtain.

The growth process can optionally be performed in a reactor or reaction space connected to the cluster tool. In a cluster tool, since each reaction space is dedicated to one type of process, the temperature of the reaction spaces within each module can be kept constant, and the reactors and reactors heating the substrate to process temperature before each run. Throughput is improved in comparison.

A stand-alone reactor is equipped with a load lock. In that case, there is no need to cool the reaction space between each run.

According to a preferred embodiment, as shown in FIG. 1, a Mo or W containing thin film is formed on a substrate by an ALD type process comprising at least one deposition cycle 10, the deposition cycle comprising:

In step 12, contacting the substrate surface with the vaporized Mo or W precursor to form up to a monolayer of Mo or W precursor on the substrate;
removing excess Mo or W precursors and reaction by-products, if any, from the surface in step 13;
In step 14, contacting the substrate surface with the vaporized chalcogen precursor;
Step 15 includes removing from the surface excess chalcogen precursor and any gaseous by-products formed in the reaction between the Mo or W precursor layer and the chalcogen precursor.

The contacting and removing steps 16 can be repeated until a desired thickness of Mo or W containing thin film is formed.

An exemplary deposition cycle begins with contacting the substrate surface with a Mo or W precursor, although in other embodiments the deposition cycle begins with contacting the substrate surface with a chalcogen precursor. Those skilled in the art will appreciate that if the substrate surface contacts the first precursor and the precursor does not react, the process begins when the next precursor is provided. In some embodiments, reactants and reaction by-products can be removed from the substrate surface by stopping the flow of the Mo or W precursor while continuing to flow an inert carrier gas such as nitrogen or argon. can.

In some embodiments, reactants and reaction byproducts can be removed from the substrate surface by stopping the flow of the second reactant while the inert carrier gas continues to flow. In some embodiments, the substrate is moved such that the different reactants alternately and sequentially contact the substrate surface in the desired order and for the desired time. In some embodiments, no removing step is performed. In some embodiments, reactants may not be removed from various portions of the chamber. In some embodiments, the substrate is moved from one portion of the chamber containing the first precursor to another portion of the chamber containing the second precursor. In some embodiments, the substrate is moved from a first reaction chamber to a second, different reaction chamber.

In some embodiments, the deposited Mo- or W-containing film may comprise a dichalcogenide thin film. In some embodiments, the deposited thin film can include molybdenum dichalcogenide or tungsten dichalcogenide. In some embodiments, the deposited thin film may comprise _MoS2 , _WS2 , _MoSe2 , _WSe2 , _MoTe2 , or _WTe2 . For simplicity, these dichalcogenides are represented as having their common stoichiometry. However, it will be appreciated that the exact stoichiometry of any Mo or W containing film or material will vary based on the oxidation state of the elements involved. Other stoichiometries are therefore expressly contemplated.

The term "dichalcogenides" is used herein and these dichalcogenides have a common stoichiometry of 1:2 ratio of metal atoms such as Mo or W to chalcogen atoms such as S, Se or Te. , the film stoichiometry can vary. For example, the ratio of metal atoms to chalcogen atoms can vary depending on the analytical technique and/or process conditions used. In some embodiments, the ratio of metal atoms to chalcogen atoms is from about 1:3 to about 2:1, preferably from about 1:2.5 to about 1:1, more preferably about 1:2. can be done. In some embodiments, the dichalcogenide film may comprise Mo or W from about 20 at% to about 50 at%, preferably from about 25 at% to about 40 at%. In some embodiments, the dichalcogenide film may comprise from about 30 at% to about 75 at%, preferably from about 35 at% to about 70 at% chalcogen (S, Se or Te).

In some embodiments, the Mo- or W-containing dichalcogenide film contains elements other than Mo, W and chalcogens, preferably Mo, W and hydrogen-containing elements other than chalcogens totaling less than about 35 at%, more preferably may contain less than about 25 at% in total. In some embodiments, the film may contain less than about 20 at% carbon, preferably less than about 15 at% carbon, and most preferably less than about 10 at% carbon. In some embodiments, the film may contain less than about 15 at% hydrogen, preferably less than about 10 at% hydrogen, and most preferably less than about 5 at% hydrogen. In some embodiments, the film may contain less than about 10 at% oxygen, preferably less than about 5 at% oxygen, and most preferably less than about 3 at% oxygen. In some embodiments, the film may contain less than about 10 at%, preferably less than about 5 at%, and most preferably less than about 3 at% of elements other than Mo or W, chalcogen, hydrogen, carbon or oxygen. Note that Mo- or W-containing films containing the above elements are also suitable for different applications such as 2D materials.

In some embodiments, the deposited Mo- or W-containing film may contain both Mo and W, although described herein as containing Mo or W for simplicity. In some embodiments, the deposited Mo- or W-containing films may contain additional elements other than Mo, W, chalcogen (S, Te or Se), oxygen, nitrogen, or silicon. In some embodiments, the deposited Mo- or W-containing films may include dopants. In some embodiments, the deposited Mo- or W-containing films may contain two or more elements from the group chalcogen (S, Te or Se), oxygen, nitrogen, or silicon. In some embodiments, the deposited Mo or W chalcogenide-containing films may contain two or more elements of the group of chalcogens (S, Te or Se). In some embodiments, thin films of the present disclosure can include any number of metals. According to some embodiments, a Mo or W containing film may contain more than one metal. In some embodiments, additional deposition phases are added to one or more deposition cycles to incorporate additional metal or metals into the Mo or W containing thin film. The additional metal phase or phases may be after the first metal phase, or after the chalcogen phase, or after both phases. In some embodiments, two or more different metal precursors can be supplied simultaneously to the same metal phase of the deposition cycle. In some embodiments, metal precursors containing different metals may be used in different deposition cycles. For example, a first metal precursor is the only metal precursor used in one or more deposition cycles, and a second metal precursor comprising a second, different metal is one or more It can be used in other deposition cycles.

Referring again to FIG. 1, some embodiments may include an optional pretreatment process in step 11 applied to the substrate surface. A pretreatment process may include one or more steps. In pretreatment, the substrate surface on which the Mo- or W-containing thin film is to be deposited may be exposed to one or more pretreatment reactants and/or specific conditions such as temperature or pressure. Pretreatment can be used for a number of reasons, including cleaning the substrate surface, removing impurities, removing native oxides, and providing the desired surface termination. In some embodiments, pretreatment includes exposing the substrate surface to one or more pretreatment reactants, such as ( _NH4 ) _2S , _H2S , HCl, HBr, _Cl2 , or HF. including. In some embodiments, the pretreatment process occurs at approximately the same temperature as the subsequent deposition process.

As described below, many different precursors can be used to deposit Mo- or W-containing thin films. Preferably, the Mo or W precursor has the formula M(thd) ₃ where M is one of Mo or W and thd is 2,2,6,6-tetramethyl-3,5 - is a heptanedionate. Preferably, the chalcogen precursor is either _H2S or _H2Se . In a preferred embodiment, the Mo or W precursor is Mo(thd) ₃ , the chalcogen precursor is _H2S and the resulting Mo or W containing thin film is _MoS2 thin film.

In some embodiments, the MoS ₂ thin film is formed on the substrate by an ALD-type process comprising at least one deposition cycle, the at least one deposition cycle comprising:

contacting the substrate surface with vaporized Mo(thd) ₃ to form a monolayer of up to Mo(thd) ₃ on the substrate;
removing excess Mo(thd) ₃ and reaction by-products, if any, from the surface;
contacting the substrate surface with vaporized _H2S ;
removing excess _H2S and any gaseous by-products formed in the reaction between the Mo(thd) ₃ layer and _H2S from the surface.

The contacting and removing steps can be repeated until a desired thickness of MoS ₂ thin film is formed.

In some embodiments, the _MoSe2 thin film is formed on the substrate by an ALD-type process comprising at least one deposition cycle, the at least one deposition cycle comprising:
contacting the substrate surface with vaporized Mo(thd) ₃ to form a monolayer of up to Mo(thd) ₃ on the substrate;
removing excess Mo(thd) ₃ and reaction by-products, if any, from the surface;
contacting the substrate surface with vaporized H ₂ Se;
removing excess _H2Se and any gaseous by-products formed in the reaction between the Mo(thd) ₃ layer and _H2Se from the surface.

The contacting and removing steps can be repeated until a desired thickness of MoSe ₂ thin film is formed.

In some embodiments, the _WS2 thin film is formed on the substrate by an ALD-type process comprising at least one deposition cycle, the at least one deposition cycle comprising:
contacting the substrate surface with vaporized W(thd) ₃ to form a monolayer of up to W(thd) ₃ on the substrate;
removing excess W(thd) ₃ and reaction by-products, if any, from the surface;
contacting the substrate surface with vaporized _H2S ;
removing excess _H2S and gaseous by-products formed in the reaction between the W(thd) ₃ layer and _H2S from the surface.

The contacting and removing steps can be repeated until a desired thickness of _WS2 thin film is formed.

In some embodiments, the _WSe2 thin film is formed on the substrate by an ALD-type process comprising at least one deposition cycle, the at least one deposition cycle comprising:
contacting the substrate surface with vaporized W(thd) ₃ to form a monolayer of up to W(thd) ₃ on the substrate;
removing excess W(thd) ₃ and reaction by-products, if any, from the surface;
contacting the substrate surface with vaporized H ₂ Se;
removing excess _H2Se and any gaseous by-products formed in the reaction between the W(thd) ₃ layer and _H2Se from the surface.

The contacting and removing steps can be repeated until a desired thickness of _WSe2 thin film is formed.

Mo or W Precursors Any of the following precursors can be used in the various ALD processes disclosed herein. In some embodiments, the Mo or W precursor is a metal organic compound. In some embodiments, the Mo or W precursor may contain at least one multidentate ligand. In some embodiments, the Mo or W precursor may contain at least one bidentate ligand. In some embodiments, the Mo or W precursor has three bidentate ligands and no other ligands. In some embodiments, the Mo or W precursor has at least one multidentate ligand attached to Mo or W via an O, N or S atom, more preferably via at least one O atom. have In some embodiments, the Mo or W precursor has at least one multidentate ligand attached to Mo or W through both O and N atoms. More preferably, β-diketonate compounds are used. In some embodiments, ketoiminate compounds are used. In some embodiments, M(acac) ₃ , M(thd) ₃ , M(tfac) ₃ , M(bac) ₃ , M(hfac) ₃ , or M(fod) ₃ compounds are used, wherein , M is Mo or W, acac is acetylacetonato or 2,4-pentanedionato, thd is 2,2,6,6-tetramethyl-3,5-heptanedionato, tfac is trifluoro acetylacetonato or 1,1,1-trifluoro-2,4-pentanedionato, bac is benzoylacetonato, C ₆ H ₅ COCHCOCH ₃ , or 1-phenyl-1,3-butanedionato, hfac is hexafluoroacetylacetonato or 1,1,1,5,5,5-hexafluoro-2,4-pentanedionato and fod is 2,2-dimethyl-6,6,7,7,8, 8,8-heptafluorooctane-3,5-dionato. In some embodiments, the Mo or W precursors are metal halide free. In some embodiments, the Mo or W precursor has two or more Mo or W atoms. In some embodiments, the Mo or W precursor has two or more Mo or W atoms and the two or more Mo or W atoms are bonded together. In some embodiments, the organometallic Mo or W precursor has at least one coordinated organic ligand and Mo or W bonded directly to oxygen that is not bonded to any other element or compound. In some embodiments, the Mo or W precursor has at least one ligand bonded to Mo or W via an O, N or S atom, preferably via at least one O atom. obtain.

In some embodiments, the Mo or W precursor may be selected from the group consisting of Mo or W β-diketonate compounds, Mo or W cyclopentadienyl compounds, Mo or W carbonyl compounds and combinations thereof. In some embodiments, the Mo or W precursor does not contain one or more metal halides. In some embodiments, the Mo or W precursor does not contain one or more metal halides that bond directly to Mo or W. In some embodiments, the Mo or W precursor does not contain one or more halogen ligands that do not bond directly to Mo or W. In preferred embodiments, the Mo or W precursor is Mo(thd) ₃ or W(thd) ₃ . In some embodiments, the Mo or W precursors do not contain carbonyl (CO) ligands. In some embodiments, the Mo or W precursor does not contain 6 carbonyl (CO) ligands. In some embodiments, the Mo or W precursor has 1, 2, 3, 4 or 5 carbonyl (CO) ligands. In some embodiments, the Mo or W precursor is a β-diketonate and is neither Mo(thd) ₃ nor W(thd) ₃ .

Mo has several oxidation states including +VI, +V, +IV, +III, +II, +I, 0, -I, and -II. W has several oxidation states, including +VI, +V, +IV, +III, +II, +I, 0, -I, and -II. In some embodiments, Mo or W in the Mo or W precursor has a +III oxidation state, eg Mo has a +III oxidation state in Mo(thd) ₃ . In some embodiments, Mo or W in the Mo or W precursor is, for example, CpMo(CO) _3Cl , _Me2Mo ( _PMe3 ) ₄ , CpW(CO) _3Cl , and _Me2W ( _PMe3 ) in ₄ has an oxidation state of +II. In some embodiments, Mo or W in the Mo or W precursor has a +I oxidation state, eg, Mo has a +I oxidation state in Mo(hfac). In some embodiments, Mo or W in the resulting thin film has a +IV oxidation state. In some embodiments, Mo or W from the Mo or W precursor is oxidized during formation of the resulting thin film. In some embodiments, for example, _Cp2MoH2 , Mo( _NMe2 ) ₄ , Mo( ^StBu ) ₄ , and Mo( _S2CNMe2 ) ₄ , or _Cp2 in _the Mo or W precursors _. It can be beneficial for Mo or W in WH ₂ , W(NMe ₂ ) ₄ , W(S ^t Bu) ₄ , W(S ₂ CNMe ₂ ) ₄ and the like to have a +IV oxidation state.

The appropriate or desirable oxidation state of Mo or W in the Mo or W precursor can depend on certain conditions and circumstances, and the optimal oxidation state of Mo or W in the Mo or W precursor in certain circumstances is , can be determined by one skilled in the art.

In some embodiments, Mo or W in the Mo or W precursor does not have an oxidation state higher than +III. In some embodiments, Mo or W in the Mo or W precursor does not have a +IV oxidation state. In some embodiments, Mo or W in the Mo or W precursor has an oxidation state of +I to +III. In some embodiments, Mo or W in the Mo or W precursor does not have oxidation states from +IV to +VI. In some embodiments, Mo or W in the Mo or W precursor does not have a +V oxidation state. In some embodiments, Mo or W in the Mo or W precursor does not have a +VI oxidation state. In some embodiments, Mo or W in the Mo or W precursor does not have a +II oxidation state. In some embodiments, Mo or W in the Mo or W precursor has a +III oxidation state. In some embodiments, Mo or W in the Mo or W precursor does not have the -II oxidation state.

Thus, in some embodiments, Mo or W in the Mo or W precursor can include oxidation states from +I to +III, and can be oxidized during formation of the resulting thin film, such as Mo or W has an oxidation state of +IV.

Without wishing to be bound by any particular theory, it is believed that the closer the oxidation state of the precursor metal to that of the deposited film, the closer to the desired phase, crystal structure, crystallinity, or orientation. Less energy and/or time is required to deposit a flexible film. Furthermore, if the precursor metal has a lower oxidation state relative to that of the metal in the deposited film, then the amount of oxygen required to deposit a film of the desired phase, crystal structure, crystallinity, or orientation is Energy or time is considered less. For example, if the metal in the deposited film has an oxidation state of +IV, the precursor metal has an oxidation state below +IV, such as +III, thus unlike typical ALD processes, the film growth It may be desirable to undergo oxidation in the film.

In some embodiments, the Mo or W precursor comprises at least one ligand that binds to Mo or W through two atoms, referred to herein as a bidentate ligand. In some embodiments, the Mo or W precursor comprises at least one bidentate ligand attached to Mo or W through at least an O, N or S atom. In some embodiments, the Mo or W precursor has at least one bidentate ligand attached to Mo or W via an O atom at a first site and a second O atom at a second site. include. In some embodiments, the Mo or W precursor comprises at least one bidentate ligand attached to Mo or W via an O atom at a first site and an N atom at a second site. In some embodiments, the Mo or W precursor comprises at least one bidentate ligand wherein the ligand is attached to Mo or W via an N atom at a first site and a second N atom at a second site. Contains ligands. In some embodiments, the Mo or W precursor comprises at least two bidentate ligands. In some embodiments, the Mo or W precursor contains three bidentate ligands.

In some embodiments, the Mo or W precursor comprises at least one bidentate ligand that is a β-diketonato ligand. In some embodiments, at least one bidentate ligand is an acac ligand. In some embodiments, at least one bidentate ligand is a thd ligand. In some embodiments, the Mo or W precursor may contain at least two β-diketonato ligands. In some embodiments, the Mo or W precursor may contain three β-diketonato ligands. In some embodiments, the Mo or W precursor may contain at least two thd ligands. In some embodiments, the Mo or W precursor may contain at least two acac ligands. In some embodiments, a Mo or W precursor may contain three thd ligands. In some embodiments, the Mo or W precursor can contain three acac ligands.

In some embodiments, the Mo or W precursors are vaporized without solvent. In preferred embodiments, the Mo or W precursors are not mixed with solvents such as organic solvents.

In some embodiments, Mo or W β-diketonates can be used in ALD type processes to deposit any kind of Mo or W containing thin films. In some embodiments, Mo or W β-diketonates can be used to deposit Mo or W elemental films, Mo or W oxide films, Mo or W nitride films, or Mo or W silicide films. Specifically, Mo(thd) ₃ and W(thd) ₃ can be used in an ALD type process to deposit any kind of Mo or W containing thin film.

In some embodiments, the Mo or W elemental thin film can be formed on the substrate by an ALD-type process comprising at least one deposition cycle, the at least one deposition cycle comprising:
contacting the substrate surface with the vaporized Mo or W β-diketonate precursor to form up to one monolayer of Mo or W β-diketonate precursor on the substrate;
removing excess Mo or W β-diketonate precursors and reaction by-products, if any, from the surface;
contacting the substrate surface with a second reactant such as _H2 or hydrogen plasma, radicals, or atoms;
removing from the surface excess second reactant and any gaseous by-products formed in the reaction between the Mo or W β-diketonate precursor layer and the second reactant.

The contacting and removing steps can be repeated until a desired thickness of Mo or W element thin film is formed.

In some embodiments, the Mo or W oxide thin film can be formed on the substrate by an ALD-type process comprising at least one deposition cycle, the at least one deposition cycle comprising:
contacting the substrate surface with the vaporized Mo or W β-diketonate precursor to form up to one monolayer of Mo or W β-diketonate precursor on the substrate;
removing excess Mo or W β-diketonate precursors and reaction by-products, if any, from the surface;
contacting the substrate surface with water, ozone, or an oxygen precursor such as oxygen plasma, radicals, or atoms;
removing from the surface excess oxygen precursor and any gaseous by-products formed in the reaction between the Mo or W β-diketonate precursor layer and the oxygen precursor.

The contacting and removing steps can be repeated until a desired thickness of Mo or W oxide thin film is formed.

In some embodiments, the Mo or W nitride thin film can be formed on the substrate by an ALD-type process comprising at least one deposition cycle, the at least one deposition cycle comprising:
contacting the substrate surface with the vaporized Mo or W β-diketonate precursor to form up to one monolayer of Mo or W β-diketonate precursor on the substrate;
removing excess Mo or W β-diketonate precursors and reaction by-products, if any, from the surface;
contacting the substrate surface with a nitrogen-containing precursor;
removing from the surface excess oxygen precursor and any gaseous by-products formed in the reaction between the Mo or W β-diketonate precursor layer and the nitrogen-containing precursor.

The contacting and removing steps can be repeated until a desired thickness of Mo or W nitride film is formed.

In some embodiments, a suitable nitrogen-containing precursor may include _NH3 . In some embodiments, a suitable precursor comprising nitrogen is a nitrogen-containing plasma, such as N plasma, N atoms, or N radicals, or N and H containing plasma, N and H containing atoms, or N and H containing radicals. can include

In some embodiments, the Mo or W silicide thin film can be formed on the substrate by an ALD-type process comprising at least one deposition cycle, the at least one deposition cycle comprising:
contacting the substrate surface with the vaporized Mo or W β-diketonate precursor to form up to one monolayer of Mo or W β-diketonate precursor on the substrate;
removing excess Mo or W β-diketonate precursors and reaction by-products, if any, from the surface;
contacting the substrate surface with a silicon-containing precursor;
removing from the surface excess silicon-containing precursor and any gaseous by-products formed in the reaction between the Mo or W β-diketonate precursor layer and the silicon-containing precursor; include.

The contacting and removing steps can be repeated until a desired thickness of Mo or W silicide film is formed.

In some embodiments, the Mo- or W-containing material is formed on a substrate in a process that includes at least one deposition cycle, which deposits the substrate by depositing a vapor phase Mo or W precursor and a second vapor phase chalcogen precursor alternately and continuously. In some embodiments, the deposition cycle may be repeated two or more times. In some embodiments, the deposition cycle may be repeated two or more times in succession. In some embodiments, after contacting the substrate with the gas phase Mo or W precursor and before contacting the substrate with the gas phase chalcogen precursor, excess Mo or W precursor and reaction by-products are removed. If there is, it can be removed. In some embodiments, excess chalcogen precursor and reaction by-products, if any, are removed after contacting the substrate with the vapor phase chalcogen precursor and before initiating another deposition cycle. can. In some embodiments, the substrate may be contacted with a purge gas after contacting the substrate with the Mo or W gas phase precursor and before contacting the substrate with the gas phase chalcogen precursor. In some embodiments, the substrate may be contacted with a purge gas after contacting the substrate with the chalcogen gas phase precursor and before initiating another deposition cycle.

Synthesis of Mo or W β-diketonate Precursors Also provided are methods of making some of the Mo or W precursors used in the ALD processes described herein. In some embodiments, precursors are synthesized having the formula M(L) ₃ where M is Mo or W and L is preferably a β-diketonato ligand, most preferably acac, hfac , or thd. In some embodiments, the Mo or W precursor synthesized has a formula of M(thd) ₃ where M is Mo or W. In some embodiments, the precursor synthesized is Mo(thd) ₃ and in other embodiments W(thd) ₃ .

In some embodiments, all handling and manipulations may be performed in an atmosphere free of air, oxygen and moisture. In some embodiments, all handling and manipulations may be performed in an inert gas atmosphere, such as _N2 or Ar atmosphere.

FIG. 2 is a process flow diagram generally illustrating a method of forming a Mo or W β-diketonate precursor 20. As shown in FIG. In some embodiments, the method of making a Mo or W β-diketonate precursor comprises:

reducing the Mo or W halide with a reducing agent in step 21 to form a first product;

subsequently adding a solvent to the first product to form a second product in step 22, thereby forming a second product MX ₃ (R ¹ ) _n , n=0-4 , where M is Mo or W, X is a halide, and R ¹ is a solvent;
forming a third product in step 23 by reacting an alkali metal compound such as BuLi, MeLi, NaH, or KH with a β-diketone;
followed by adding a third product to the second product in step 24, thereby forming a compound of the formula M(L) ₃ , where M is Mo or W and L is a β-diketonato ligand ) in step 25.

In some embodiments, the Mo or W halide of step 21 is preferably an anhydrous Mo or W halide. In some embodiments, the Mo or W halide of step 21 has the formula MX ₅ , where M is Mo or W and X is the halide, preferably Cl. In some embodiments, the metal halide of step 21 can have the formula MX ₄ or MX ₆ , where M is W and X is a halide. In some embodiments, the Mo or W halide of step 21 is added to the solvent prior to reduction with a reducing agent, preferably an organic solvent such as ether. In preferred embodiments, the solvent is _Et2O .

In some embodiments, the reducing agent comprises a metal such as metal Sn. In some embodiments, the reducing agent is an organic species, preferably a bis(trialkylsilyl) six-membered ring system or related compounds such as 1,4-bis(trimethylsilyl)-1,4-dihydropyrazine (DHP). include. Preferably, the reducing agent is provided in the form of powder or pellets such as Sn pellets. In some embodiments, reducing the Mo or W halide comprises adding a reducing agent to a solution comprising the Mo or W halide to form the first product. In a preferred embodiment, reducing the Mo or W halide is by adding Sn pellets to a solution of MCl ₅ in Et ₂ O to MCl ₄ (Et ₂ O) ₂ , where M is Mo or W is).

In some embodiments, the mixture of Mo or W halide and reducing agent is stirred for a first duration. In some embodiments, the mixture is stirred until the reaction is complete. After formation of the desired first product comprising MCl ₄ (Et ₂ O) ₂ , where M is Mo or W, the mixture can be allowed to settle. In some embodiments, after the reaction is complete, the first product is separated and isolated from any solvent, by-products, excess reactants, or any other compounds that are undesirable in the first product. can let go

In some embodiments, solvent is added to the first product to form the second product. In preferred embodiments, the solvent is THF. In some embodiments, the mixture is stirred for a second duration. In some embodiments, the mixture is stirred until the reaction is complete. After the desired second product is formed, the mixture can be allowed to settle. In some embodiments, after the reaction is complete, the second product is separated and isolated from any solvent, by-products, excess reactants, or any other compounds that are undesirable in the second product. can let go In a preferred embodiment, forming the second product comprises adding THF to the first product to form MCl ₃ (THF) ₃ , where M is Mo or W can include

In some embodiments, the second product MoCl ₃ (THF) ₃ is prepared according to Stoffelbach et al. . J. Inorg. Chem. 10/2001: 2699-2703, which is incorporated herein by reference in its entirety.

In some embodiments, the third product is formed by reacting an alkali metal compound with a β-diketone. In preferred embodiments, the alkali metal compound comprises butyllithium. In some embodiments, alkali metal compounds can include, for example, KH, NaH, or MeLi. In some embodiments, the alkali metal compound may be provided as an alkane solution, preferably a hexane solution. In some embodiments, an alkali metal compound may be added to the solvent. In some embodiments, the solvent can include heterocyclic solvents. In preferred embodiments, the solvent is THF.

In some embodiments, the β-diketone compound is Hthd, Hacac, Htfac (where Htfac is trifluoroacetylacetone), Hfod (where fod is 2,2-dimethyl-6,6,7,7, 8,8,8-heptafluoro-3,5-octanedione), or Hhfac, preferably Hthd. In some embodiments, reacting an alkali metal compound with a β-diketone compound comprises formula M ¹ L, wherein M ¹ is an alkali metal , and L is a β-diketonato ligand). In a preferred embodiment, butyllithium in hexane is added to THF to form a solution. Hthd is then added to the solution to react with the butyllithium, thereby forming a third product containing Lithd.

In some embodiments, the solution is optionally cooled before, during, and/or after the reaction is complete. In some embodiments, the β-diketone compound may be cooled prior to adding the alkali metal compound. In some embodiments, the solution may be stirred until the reaction is complete. In some embodiments, any gaseous by-products produced by the reaction may be vented, for example, via a bubbler.

In some embodiments, a _third product is added to the second product, thereby resulting in a Mo or form a Wβ-diketonate precursor. In some embodiments, the second product may be added to the solvent before adding the third product. In preferred embodiments, the solvent is THF. In some embodiments, the Mo or W β-diketonate precursor is formed by adding a third product to the mixture. In some embodiments, the third product can have the formula M ¹ L, where M ¹ is an alkali metal and L is a β-diketonato ligand. In some embodiments, the third product may comprise a solution containing the third product. In a preferred embodiment, Lithd is added to a THF suspension of MCl ₃ (THF) ₃ thereby forming M(thd) ₃ (where M is Mo or W).

In some embodiments, the second product may be cooled before adding the third product. In some embodiments, the mixture is warmed to room temperature after the third product is added. In some embodiments, the mixture is stirred for a second duration. In some embodiments, the mixture is stirred until the reaction is complete.

After the reaction is substantially complete, the final product can be separated and isolated from any solvent, by-products, excess reactants, or any other compounds that are undesirable in the final product.

In some embodiments, the method of making a Mo or W β-diketonate precursor comprises:
reducing anhydrous MoCl ₅ with Sn to form a first product in step 21;
Subsequently, adding a solvent comprising tetrahydrofuran (THF) to the first product to form a second product MoCl ₃ (THF) ₃ in step 22, thereby forming a second product MoCl ₃ forming (THF) ₃ ;
forming a third product Lithd in step 23 by reacting butyllithium with Hthd;
This is followed by adding a third product Lithd to the second product MoCl ₃ (THF) ₃ in step 24 thereby forming precursor Mo(thd) ₃ in step 25 .

Example 1
Mo(thd) ₃ was synthesized by the following process. All handling and manipulation was performed with strict exclusion of air and moisture using standard Schlenk techniques and an inert gas ( _N2 or Ar) glove box.

First, 5.00 g (18.3 mmol) of anhydrous MoCl ₅ and 10 g (84 mmol) of Sn pellets were suspended in 50 ml of Et ₂ O. The mixture was stirred at room temperature for 1 hour to form a solution and a solid. The solids were allowed to settle to the bottom of a Schlenk bottle and most of the Et ₂ O solution was removed using Ar pressure and a Teflon capillary tube.

Then 50 ml of THF was added and the mixture was stirred at room temperature for 3 hours to form solid MoCl ₃ (THF) ₃ . MoCl ₃ (THF) ₃ was separated from excess Sn by transferring the THF/MoCl ₃ (THF) ₃ suspension to another Schlenk bottle using Ar pressure and a Teflon capillary tube. Solid MoCl ₃ (THF) ₃ was then filtered from the suspension using a Schlenk sinter and washed with Et ₂ O.

Next, a Lithd solution was prepared. 30 ml of THF was cooled in a CO ₂ /acetone bath and 4.48 ml of 1.6 BuLi in hexane was added. Then 1.321 g (7.168 mmol) of Hthd was slowly added to this solution using a syringe. The solution was then stirred at room temperature for 2 hours. Gaseous by-products were vented from the Schlenk flask containing the solution through a mercury bubbler.

Solid MoCl ₃ (THF) ₃ was then suspended in 20 ml THF. The suspension was then cooled with a CO ₂ /acetone bath and the previously prepared Lithd solution was added using a Teflon capillary and Ar pressure. The resulting solution was warmed to room temperature and stirred overnight.

The THF solvent was then evaporated using a water bath and vacuum. The solid product obtained was transferred to a sublimation apparatus and sublimed at 160° C.-180° C. and 0.5 mbar. The resulting Mo(thd) ₃ sublimate was collected in a glove box.

The synthesized compounds were analyzed using mass spectrometry. As shown in FIG. 3, a molecular ion with an isotopic pattern corresponding to Mo(thd) ₃ is found at m/z 647. In addition to Mo(thd) ₃ , fragment ions with oxygen, such as [Mo(thd) ₂ O ₂ ] ⁺ , [Mo(thd)O] ⁺ , [Mo(thd) ₂ O ₂ -Bu] ⁺ , and [Mo(thd)O ₂ ] ⁺ etc. are seen. However, these peaks are likely due to exposure of the Mo(thd) ₃ compound to air during sample introduction into the mass spectrometer.

The molecular structure of the synthesized compound was analyzed using single crystal X-ray diffraction (SCXRD). The structures of the synthesized Mo(thd) ₃ compounds are illustrated in FIG.

Mo(acac) ₃ and Mo(hfac) ₃ were also synthesized using procedures similar to those used to synthesize Mo(thd) ₃ . Hacac and Hhfac were used instead of Hthd to synthesize Mo(acac) ₃ and Mo(hfac) ₃ respectively. Thermogravimetric analysis (TGA) was used to investigate the thermal properties of the three Moβ-diketonate compounds. As shown in FIG. 5, the thermogravimetric curves of Mo(thd) ₃ and Mo(hfac) ₃ show the evaporation of these compounds with increasing temperature, and the thermogravimetric curve of Mo(acac) ₃ is It shows that this compound is mainly decomposed as the temperature increases.

Chalcogen Precursors It will be appreciated by those skilled in the art that many chalcogen precursors can be used in the ALD processes disclosed herein. In some embodiments, the chalcogen precursor is selected from the list below. _H2S , _H2Se , _H2Te , ( _CH3 ) _2S , (NH4)2S, dimethylsulfoxide ((CH3)2SO), ( _CH3 ) _2Se , ( _CH3 ) _2Te , elements or atoms S, Se, Te, other precursors containing chalcogen-hydrogen bonds, such as H ₂ S ₂ , H ₂ Se ₂ , H ₂ Te ₂ , or formula RYH, where R is substituted or unsubstituted hydrocarbon, preferably C ₁ -C ₈ alkyl or substituted alkyl, such as alkylsilyl group, more preferably linear or branched C ₁ -C ₅ alkyl group, etc., and Y is S , Se or Te). In some embodiments, the chalcogen precursor has the formula R—S—H, where R is a substituted or unsubstituted hydrocarbon, preferably a C1-C8 alkyl group, more preferably linear or branched can be a C ₁ -C ₅ alkyl group having the shape of a thiol. In some embodiments, the chalcogen precursor has the formula (R ₃ Si) ₂ Y, where R ₃ Si is an alkylsilyl group and Y can be Se or Te. In some embodiments, the chalcogen precursor comprises S or Se. In some preferred embodiments, the chalcogen precursor comprises S. In some embodiments, the chalcogen precursor may include elemental chalcogen, such as elemental sulfur. In some embodiments, the chalcogen precursor is Te free. In some embodiments, the chalcogen precursor comprises Se. In some embodiments, the chalcogen precursor is selected from precursors containing S, Se or Te. In some embodiments, the chalcogen precursor comprises H ₂ S _n , where n is 4-10.

Suitable chalcogen precursors can include many chalcogen-containing compounds, so long as they contain at least one chalcogen-hydrogen bond. In some embodiments, the chalcogen precursors can include chalcogen plasma, chalcogen atoms, or chalcogen radicals. In some embodiments where an excited chalcogen precursor is desired, a plasma may be generated within or upstream of the reaction chamber. In some embodiments, the chalcogen precursor does not include excited chalcogen precursors such as plasma, atoms or radicals. In some embodiments, the chalcogen precursors may comprise chalcogen plasmas, chalcogen atoms or chalcogen radicals formed from chalcogen precursors containing chalcogen-hydrogen bonds such as H ₂ S. In some embodiments, the chalcogen precursor may comprise a chalcogen plasma, a plasma containing chalcogen atoms or chalcogen radicals such as sulfur, selenium or tellurium, preferably a plasma containing sulfur. In some embodiments, the plasma, atoms, or radicals comprise tellurium. In some embodiments the plasma, atoms or radicals comprise selenium.

Example 2
Various deposition experiments using MoCl ₅ and H ₂ S as precursors at reaction temperatures between 150° C. and 500° C. in a flow-type reactor (ASM America F-120 reactor) without residence time of the precursors. did Various substrates were used such as Al ₂ O ₃ , ZnS, soda lime glass, Si, and Ir. Neither Mo nor S were detected on the substrate in amounts that would indicate film growth after the film deposition experiments were performed. EDX was performed on the sample and showed only traces of Mo. No S was detected on the sample. This process is reported in Browning et al., "Atomic layer deposition of _MoS2 thin films," which is incorporated herein by reference in its entirety. We performed similar experiments under conditions reasonably similar to those described in the Browning paper, but the tests were unsuccessful, presumably due to the non-robustness of the process disclosed therein. showed sex.

Example 3
MoS ₂ thin films were deposited according to the ALD process disclosed herein utilizing Mo(thd) ₃ as the Mo precursor and H ₂ S as the chalcogen precursor. MoS ₂ was deposited on silicon, titanium disulfide, alumina, and soda lime glass substrates. The substrate was contacted with alternating pulses of Mo(thd) ₃ and H ₂ S at deposition temperatures ranging from about 175°C to about 500°C.

No deposition of MoS ₂ was observed at deposition temperatures between 175°C and 350°C. The amount of film on the substrate appeared to increase at deposition temperatures above about 375°C. The highest growth rate was achieved at a deposition temperature of approximately 500°C. At this deposition temperature, the substrate was covered with a purple or brown MoS ₂ film.

The MoS ₂ films obtained were characterized by FESEM and the morphology of the films was found to be substantially the same regardless of the substrate on which the films were deposited. A flaky structure was observed on the surface of some of the films, but cross-sectional FESEM images revealed that the films were dense and free of cracks and pinholes, as shown in FIG.

As shown in FIG. 7, the growth rate of ALD MoS ₂ films saturated at about 0.2 Å/cycle for both Mo(thd) ₃ and H ₂ S pulse lengths of about 0.5-1 s. . Film thickness was observed to increase substantially linearly, as shown in FIG. 8, although there may be an incubation period as indicated by the slightly steeper slope after 500 deposition cycles. .

Increasing the Mo(thd) ₃ pulse length did not affect the growth rate, but the film morphology was affected. FIG. 9 illustrates that films deposited with 0.2 second and 0.5 second pulses have nearly identical surfaces containing sharp platelet-like structures. Mo(thd) ₃ pulse lengths of 1 s or longer resulted in particle-laden surfaces, although no difference in film thickness was observed. The resulting films were deposited using 1000 deposition cycles, whereas 2000 cycles of films deposited using Mo(thd) ₃ pulse lengths of 0.2 s, 0.5 s and 1 s A similar surface structure was also observed with a Mo(thd) ₃ pulse length of 4 s when compared to the deposited films. Therefore, the Mo(thd) ₃ pulse length is also likely to have an effect, so the film thickness can affect the structural difference of the surface.

Varying the H ₂ S pulse length produced similar differences in the film surface structure, but here a shorter H ₂ S pulse length resulted in a flake-free surface. As shown in Figure 10, a _H2S pulse length of 0.2 seconds resulted in a film with a surface containing particles. Longer pulses resulted in surfaces containing flakes with sharp edges.

MoS ₂ film growth was visually analyzed for MoS ₂ films deposited from 10 to 2000 deposition cycles. Mo(thd) ₃ was used as Mo precursor with a pulse time of 0.5 sec and purge time of 1 sec, while _H2S was used as chalcogen precursor with a pulse time of 0.5 sec and purge time of 1 sec. bottom. The deposition temperature for all samples was 500°C. FIG. 11A illustrates MoS ₂ films deposited between 10 and 50 cycles, and FIG. 11B shows MoS ₂ films deposited between 100 and 2000 cycles. The surface structure of the film is crystalline and the presence of sharp flakes on the film surface, which appears to be nearly flat up to approximately 1500 deposition cycles, appears to be thickness dependent. After 2000 deposition cycles, the raised flaky structures cover the entire surface of the film.

The composition of the deposited _MoS2 films was analyzed by EDX. The theoretical film composition of Mo ₃₅ S ₆₅ was obtained by synthesizing spectra of theoretical samples consisting of MoS ₂ films on silicon substrates using Oxford INCA software. The composition of MoS ₂ films deposited at 500° C. was analyzed by EDX while changing the Mo(thd) ₃ pulse length, as shown in FIG. 12A. The composition of the MoS ₂ film deposited at 500° C. was analyzed by EDX while varying the H ₂ S pulse length, as shown in FIG. 12B. In both cases, the measured _MoS2 film composition was determined to be similar to the theoretical composition.

The element ratios of the MoS2 film sample deposited at 500° C. by the ALD process were also measured and illustrated in FIG. The MoS2 films were deposited by an ALD process with 250-2000 deposition cycles. As the number of deposition cycles increased, the measured elemental proportions of MoS2 films went from Mo-rich to S-rich. A MoS2 sample deposited by an ALD process with 2000 deposition cycles had _a measured composition of _Mo42S58 . Although there may be an incubation period, the deposited film thickness was observed to increase approximately linearly, as illustrated in FIG.

The composition of two sets of deposited _MoS2 film samples was analyzed by grazing incidence X-ray diffraction (GIXRD), as illustrated in FIG. A set of sample MoS ₂ films were deposited by an ALD process in which the Mo precursor pulse time was varied from 0.2 seconds to 4 seconds while the sulfur precursor pulse was kept constant at 0.5 seconds. A second set of sample MoS ₂ films were deposited by an ALD process in which the sulfur precursor pulse time was varied from 0.2 seconds to 2 seconds while the Mo precursor pulse was kept constant at 0.5 seconds. The samples were deposited at 500°C. The intensity of the (002) peak shown in FIG. 14 increased with decreasing Mo precursor pulse time and increased with increasing sulfur precursor pulse time.

Raman spectroscopy was used to identify the phases of the deposited films. MoS ₂ has characteristic peaks at 383 cm ⁻¹ for in-plane vibrations of Mo and S atoms and at 406 cm ⁻¹ for out-of-plane vibrations of S atoms. Both these peaks of the deposited _MoS2 thin film are clearly visible, as shown in FIG.

The phases of two sets of deposited _MoS2 film samples were analyzed using Raman spectroscopy, as illustrated in FIG. A set of sample MoS ₂ films were deposited by an ALD process in which the Mo precursor pulse time was varied from 0.2 seconds to 4 seconds while the sulfur precursor pulse was kept constant at 0.5 seconds. A second set of sample MoS ₂ films were deposited by an ALD process in which the sulfur precursor pulse time was varied from 0.2 seconds to 2 seconds while the Mo precursor pulse was kept constant at 0.5 seconds. The samples were deposited at 500°C. The in-plane and out-of-plane MoS ₂ peak intensities were observed to increase with decreasing Mo precursor pulse time and were observed to increase with increasing sulfur precursor pulse time.

The elemental composition of two _MoS2 thin film samples deposited by the ALD process was investigated using X-ray photoelectron spectroscopy (XPS), as illustrated in FIG. One sample was deposited by an ALD process with a 0.2 second Mo precursor pulse, while a second sample was deposited by an ALD process with a 4 second Mo precursor pulse time.

The surface roughness of MoS ₂ film samples deposited by ALD process using Mo(thd) ₃ as Mo precursor and having 10-50 deposition cycles, as exemplified in FIG. AFM). The roughness of the samples deposited by 10 cycles and 50 cycles was found to be 0.41 nm, while the roughness of the samples deposited by 25 cycles was found to be 0.44 nm. The surface features of the films were less than 10 nm in size for all samples, but the size of the surface features appeared to increase with the number of deposition cycles.

FIG. 19 illustrates the growth rate and elemental proportions of MoS ₂ films deposited at temperatures between 425° C. and 500° C. by an ALD process using Mo(thd) ₃ as the Mo precursor. The growth rate was observed to increase with increasing deposition temperature, with the highest growth rate observed at a deposition temperature of 500°C. The composition of the deposited film changed depending on the deposition temperature.

MoS ₂ film growth was visually analyzed for the MoS ₂ films deposited by ALD, as illustrated in FIG. Mo(thd) ₃ was used as Mo precursor with a pulse time of 0.5 sec and purge time of 1 sec, while _H2S was used as chalcogen precursor with a pulse time of 0.5 sec and purge time of 1 sec. bottom. The film formation temperature was varied from 350.degree. C. to 500.degree.

2D Materials The ALD processes described herein are used to deposit 2D materials comprising Mo or W, such as _MoS2 , _WS2 , MoSe2, or WSe2 2D materials such as MoS2, _WS2 , _MoSe2 , or WSe2 dichalcogenides. obtain. A 2D material, also called a monolayer material, is a material that consists of a single connected monolayer. Although the 2D material forms a single connected monolayer, multiple monolayers can be deposited by the deposition processes disclosed herein. For example, for 2D _MoS2 , the 2D material comprises a single layer of covalently bonded MoS2 molecules arranged such that one layer of Mo atoms is sandwiched between _two layers of S atoms. The basic atomic structure of MoS ₂ will be familiar to those skilled in the art.

Such special features make the 2D materials super useful, for example, as lubricants in optoelectronics, spintronics, and valleytronics, for use as catalysts, chemical and biological sensors in THz generation and detection. It is useful in a wide range of potential applications such as capacitors, LEDs, solar cells, lithium-ion batteries, as well as MOSFET channel materials.

Unlike other 2D materials such as graphene, 2D Mo or W dichalcogenides have unique electronic properties that make them useful for miniaturization of semiconductor devices. For example, unlike graphene, 2D Mo or W dichalcogenides have a direct bandgap and are semiconducting. Mo or W dichalcogenides are therefore useful in electronic devices, for example Mo or W dichalcogenides can be used as channel materials in gate stacks or transistors.

According to some embodiments, 2D materials comprising Mo or W can be deposited by ALD according to the methods disclosed herein. In some embodiments, the 2D material comprising Mo or W may comprise 10 monolayers or less, preferably 5 monolayers or less, most preferably 3 monolayers or less of the Mo or W containing compound.

In some embodiments, a 2D material comprising Mo or W may comprise 10 monolayers or less, preferably 5 monolayers or less, and most preferably 3 monolayers or less of Mo or W dichalcogenides. In some embodiments, the 2D material comprising Mo or W comprises no more than 10 monolayers of _MoS2 , _WS2 , MoSe2, _{WSe2 , MoTe2} , or _WTe2 , preferably less than 5 monolayers, most Preferably it may contain no more than 3 monolayers.

In some embodiments, a method of depositing a 2D material comprising Mo or W on a substrate can include an ALD process involving multiple cycles, as disclosed herein. In some embodiments, the method of depositing a 2D material comprising Mo or W comprises 500 deposition cycles or less, preferably 200 deposition cycles or less, most preferably 100 deposition cycles or less, as disclosed herein. It can include ALD processes including film cycles and following. As can be selected by one of ordinary skill in the art depending on the specific precursors, substrates and process conditions, methods for depositing 2D materials comprising Mo or W on substrates, as disclosed herein, are 50 cycles or less. , 25 cycles or less, 15 cycles or less, or 10 cycles or less.

In some embodiments, the deposited 2D material comprising Mo or W is less than 10 nm, more preferably less than 5 nm, more preferably less than 3 nm, more preferably less than 2 nm, more preferably less than 1.5 nm, and Most preferably it can be less than 1.0 nm.

In some embodiments, the deposited 2D material has a roughness (R _q ) of less than about 0.75 nm, preferably less than about 0.5 nm, and most preferably less than or equal to about 0.4 nm. Roughness can be measured, for example, by atomic force microscopy (AFM) or X-ray reflection (XRR). For ultra-thin 2D material films, AFM may be the preferred method.

In some embodiments, 2D materials comprising Mo or W can be used as channel materials in electronic devices, such as gate stacks. In some embodiments, a 2D material containing Mo or W can be deposited after the gate dielectric, i.e., channel last. In some embodiments, 2D materials including Mo or W can be deposited before the gate dielectric, ie, channel-first. In some embodiments, the gate stack may be fabricated upside down such that the channel is above the gate in the gate stack.

FIG. 21 is an aberration-corrected scanning tunneling electron microscope (AC-STEM) image of a MoS ₂ thin film 1420 deposited on a silicon substrate 1400 containing native oxide 1410. FIG. Silicon atoms 1401 of substrate 1400 are seen as white dots in the bottom half of the image, while native oxide 1410 is the darker layer between MoS ₂ thin film 1420 and silicon substrate 1400 . The MoS ₂ shown here is about 2-3 monolayers and has a thickness of about 10-15 Å. The spacing between monolayers is about 6-8 Å, which is within the expected range for _MoS2 .

The terms "film" and "thin film" are used herein for brevity. "Film" and "thin film" are intended to mean any continuous or discontinuous structures and materials deposited by the methods disclosed herein. "Films" and "thin films" include, for example, 2D materials, nanorods, nanotubes or nanoparticles, or flat single partial or complete molecular layers, or partial or complete atomic layers, or atoms and and/or clusters of molecules. "Films" and "thin films" may include materials or layers that have pinholes but are still at least partially continuous.

The term chalcogen as used herein is intended to refer primarily to the chemical elements of sulfur, selenium and tellurium, although in some cases the term refers to oxygen, as will be apparent to those skilled in the art. There is also Similarly, the terms chalcogenide and dichalcogenide are intended to refer primarily to sulfides, selenides, and tellurides, although in some cases such terms may also refer to oxides, as will be apparent to those skilled in the art. It can also refer to things.

While the foregoing invention has been described with respect to certain preferred embodiments, other embodiments will be apparent to those skilled in the art. Additionally, other combinations, omissions, permutations and modifications will be apparent to those skilled in the art in view of the disclosure herein. Accordingly, the invention is not intended to be limited by reciting the preferred embodiments, but is instead defined by reference to the appended claims.

Claims (46)

A process comprising at least one cycle of forming a Mo or W containing thin film on a substrate within a reaction chamber, said cycle comprising:
contacting said substrate with a gas phase Mo or W precursor such that at most a first Mo or W precursor monolayer is formed on the substrate surface, said Mo or W precursor Mo or W in the body has an oxidation state below +IV but not 0;
removing excess Mo or W precursors and reaction by-products, if any;
contacting the substrate with a vapor phase chalcogen precursor, the chalcogen precursor reacting with the Mo or W precursor on the substrate surface;
removing excess chalcogen precursor and reaction by-products, if any;
optionally repeating the contacting and removing steps until a desired thickness of Mo or W containing thin film is formed. 3. The process of claim 1, wherein the process is an atomic layer deposition (ALD) process. 2. The process of claim 1, wherein said process comprises two or more consecutive cycles. 2. The process of claim 1, wherein the Mo or W containing thin film is a Mo or W sulfide, selenide, or telluride thin film. 2. The process of claim 1, wherein the oxidation state of Mo or W in the Mo or W precursor is +III. 2. The process of claim 1, wherein the chalcogen precursor comprises _H2S , _H2Se , _H2Te , ( _CH3 ) _2S , ( _CH3 ) _2Se , or ( _CH3 ) _2Te . An atomic layer deposition (ALD) process comprising at least one cycle of forming a Mo or W sulfide, selenide, or telluride thin film on a substrate in a reaction chamber, said cycle comprising:
contacting said substrate with a gas phase Mo or W precursor such that at most a first Mo or W precursor monolayer is formed on the substrate surface, said Mo or W precursor contacting, wherein the body comprises at least one bidentate ligand;
removing excess Mo or W precursors and reaction by-products, if any;
contacting the substrate with a vapor phase chalcogen precursor, the chalcogen precursor reacting with the Mo or W precursor on the substrate surface;
removing excess chalcogen precursor and reaction by-products, if any;
repeating said contacting and said removing steps until a desired thickness of Mo or W containing thin film is formed. 8. The process of claim 7, wherein the bidentate ligand binds to the Mo or W atom through an O, S, or N atom. 9. The process of claim 8, wherein the bidentate ligand binds to the Mo or W atom through two O atoms. 9. The process of claim 8, wherein the bidentate ligand binds to the Mo or W atom via O and N atoms. 9. The process of claim 8, wherein the bidentate ligand binds to the Mo or W atom through two N atoms. 8. The process of claim 7, wherein said bidentate ligand is a β-diketonato ligand. 13. The process of claim 12, wherein the β-diketonato ligand is an acetylacetonato (acac) ligand. 13. The process of claim 12, wherein the β-diketonato ligand is a 2,2,6,6-tetramethyl-3,5-heptanedionato (thd) ligand. 8. The process of claim 7, wherein said Mo or W precursor comprises at least two bidentate ligands. 8. The process of claim 7, wherein the Mo or W precursor contains three bidentate ligands. An atomic layer deposition (ALD) process comprising at least one cycle of forming a Mo or W sulfide, selenide, or telluride 2D material on a substrate in a reaction chamber, said cycle comprising:
contacting said substrate with a gas phase Mo or W precursor such that at most a first Mo or W precursor monolayer is formed on the substrate surface, said Mo or W precursor the body is Mo or W beta-diketonate;
removing excess Mo or W precursors and reaction by-products, if any;
contacting the substrate with a vapor phase sulfur, selenium, or tellurium precursor, wherein the sulfur, selenium, or tellurium precursor reacts with the Mo or W precursor on the substrate surface; and
removing excess sulfur or selenium precursors and reaction by-products, if any. 18. The process of claim 17, wherein the Mo or W containing thin film is a Mo or W sulfide, selenide, or telluride thin film. 18. The process of claim 17, wherein the oxidation state of Mo or W atoms comprising said Mo or W precursor is +III. 18. The process of claim 17, wherein the chalcogen precursor comprises _H2S , _H2Se , _H2Te , ( _CH3 ) _2S , ( _CH3 ) _2Se , or ( _CH3 ) _2Te . 18. The process of claim 17, wherein the Mo or W precursor is Mo(thd) ₃ and the chalcogen precursor is _H2S . 18. The process of claim 17, wherein the Mo or W precursor is W(thd) ₃ and the chalcogen precursor is _H2S . 18. The process of claim 17, wherein said 2D material comprises _MoS2 . A method of making a Mo or W β-diketonate precursor, said method comprising:
A first reactant having the formula MX ₃ (R) _n , where n is a number from 0 to 4, M is Mo or W, X is a halide, and R is a solvent. and
forming a first product by reacting an alkali metal compound with a β-diketone compound;
The first product is then added to the first reactant, thereby having the formula ML ₃ , where M is Mo or W and L is a β-diketonato ligand. forming a Mo or W β-diketonate precursor. Providing the first reactant comprises:
reducing the Mo or W halide with a reducing agent to form a first intermediate product;
25. The method of claim 24, further comprising subsequently adding a solvent to said first product to form a second intermediate product thereby forming said first reactant. 25. The method of claim 24, wherein the Mo or W halide is _MoCl5 , the β-diketone compound is Hthd, and the Mo or W β-diketonate precursor formed is Mo(thd) ₃ . . A method of forming a Mo or W β-diketonate compound, wherein Mo or W in said Mo or W β-diketonate compound has an oxidation state of +III, said method comprising:
A first reactant having the formula MX ₃ (R) _n , where n is a number from 0 to 4, M is Mo or W, X is a halide, and R is a solvent. and
forming a first product by reacting an alkali metal compound with a β-diketone compound;
The first product is then reacted with the first reactant, thereby forming a compound of the formula ML ₃ , where M is Mo or W with an oxidation state of +III and L is a β-diketonato linkage. forming a Mo or W β-diketonate compound with the A process comprising at least one deposition cycle for forming a Mo- or W-containing material on a substrate within a reaction chamber, said deposition cycle comprising:
alternately and sequentially contacting the substrate with a vapor phase Mo or W precursor and a second vapor phase chalcogen precursor;
The process wherein Mo or W in said Mo or W precursor has an oxidation state below +IV but not 0. 29. The process of Claim 28, wherein the deposition cycle is repeated two or more times. after contacting the substrate with the gas phase Mo or W precursor and before contacting the substrate with the gas phase chalcogen precursor if there is excess Mo or W precursor and reaction by-products 29. The process of claim 28, further comprising removing it. removing excess chalcogen precursor and reaction by-products, if any, after contacting the substrate with the vapor phase chalcogen precursor and before initiating another deposition cycle; 29. The process of claim 28, further comprising. 4. The method of claim 1, further comprising contacting the substrate with a purge gas after contacting the substrate with the Mo or W gas phase precursor and prior to contacting the substrate with the gas phase chalcogen precursor. 28. The process according to 28. 29. The process of claim 28, further comprising contacting the substrate with a purge gas after contacting the substrate with the vapor phase chalcogen precursor and before initiating another deposition cycle. Claim 28, further comprising subjecting the substrate to a vacuum after contacting the substrate with the Mo or W gas phase precursor and prior to contacting the substrate with the gas phase chalcogen precursor. process described in . 29. The process of claim 28, further comprising exposing the substrate to a vacuum after contacting the substrate with the vapor phase chalcogen precursor and before initiating another deposition cycle. 29. The process of claim 28, wherein said Mo or W containing material comprises Mo or W elements. 29. The process of claim 28, wherein the Mo or W containing material comprises a Mo or W oxide material. 29. The process of claim 28, wherein the Mo or W containing material comprises a Mo or W nitride material. 29. The process of claim 28, wherein the Mo or W containing material comprises a Mo or W silicide material. 29. The process of claim 28, wherein the deposition cycle forms up to a monolayer of Mo or W containing material on the substrate. 29. The process of claim 28, wherein the deposition cycle forms about 50% or less of a monolayer of Mo or W containing material on the substrate. 29. The process of claim 28, wherein the deposition cycle forms about 25% or less of a monolayer of Mo or W containing material on the substrate. 29. The process of claim 28, wherein the deposition cycle forms about 10% or less of a monolayer of Mo or W containing material on the substrate. 29. The process of claim 28, further comprising subjecting the substrate to a pretreatment process prior to forming the Mo or W containing material on the substrate. 29. The process of claim 28, wherein said second vapor phase chalcogen precursor comprises plasma. 46. The process of claim 45, wherein said plasma is formed from compounds containing -SH bonds.

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